This invention relates to a cellulose fiber exhibiting excellent antibacterial effects and a production process thereof.
From the viewpoints of a tendency toward cleanliness as a social phenomenon and a demand for sophisticated medical technology, antibacterial materials have attracted attention, and they have been important in, for example, the household field and the medical field.
Among these, textile goods are widely used in everyday use clothing and medical materials, and there is a great demand for fiber materials having antibacterial effects.
In the above-mentioned milieu, research and developments of fiber materials having antibacterial effects have become activated. For example, reported are a disinfectant polymer composition comprising a zeolite onto which metal ions are fixed (Japanese Patent Laid-open No. 59-133235), disinfectant fiber comprising iodine in an amount effective to exhibit disinfectant effects (Japanese Patent National Publication No. 61-500500), a resin composition comprising a combination of antibacterial zeolite and a discoloration-preventing agent (Japanese Patent Laid-open No. 63-265958), and an antibacterial acrylic fiber comprising a zeolite onto which metal ions are fixed. In particular, an antibacterial fiber product using a silver-based antibacterial agent and hydrogen peroxide (Japanese Patent Laid-open No. 7-109672), a fiber using a silver-based antibacterial agent and a particular aromatic compound for preventing coloring (Japanese Patent Laid-open No. 8-325844), and a synthetic fiber having a two-layer structure using a silver-based antibacterial agent (Japanese Patent Laid-open No. 9-87928) attract attention.
As described above, various fiber materials having characteristics of antibacterial effects are known, and a heavy metal-based inorganic antibacterial agent is primarily used as an antibacterial agent, and especially, a silver-based inorganic antibacterial agent is widely used. In general, a silver-based antibacterial agent has advantages, such as a high degree of safety to humans, antibacterial effects on various bacteria, a long-term duration of antibacterial effects, and excellent thermal resistance. However, there are problems in that uniform incorporation into a fiber is difficult in many cases, yarns are likely to be snapped during a spinning process, the texture of a fiber surface deteriorates, and the strength of the fiber is decreased.
As a host fiber material, synthetic fiber is mostly used. Using synthetic fiber such as polyester, polyamide, and polypropylene, a fiber containing a silver-based antibacterial agent is produced by melt-spinning after a silver-based antibacterial agent is added to molten resin or by melt-spinning of master pellets of synthetic resin to which a silver-based antibacterial agent is added. Such antibacterial fibers are widely used in fiber products such as non-weave textile, cloth, and filters, and some of them are used in medical products. However, they are not satisfactory products due to problems in moisture and water absorbency.
On the other hand, a natural fiber such as cotton does not exhibit sufficient antibacterial effects due to its constituent components. Further, a cellulose fiber such as rayon cannot possess antibacterial effects because chemical components used in the viscose production process decompose silver-based antibacterial agents. By using a binder, it is possible to fix a silver-based antibacterial agent on the surface of a cellulose fiber such as rayon. However, due to the binder, a texture of the fiber and moisture absorbency greatly deteriorate, and washing durability is poor, i.e., very little practical use is realized.
Cellulose fiber has been known as artificial fiber for some time, and had been manufactured and used widely until synthetic fiber was developed. In recent years, demand for cellulose fiber has been declined due to all-purpose characteristics of synthetic fiber, and cellulose fiber has been ignored. However, recently, cellulose fiber has been attractive as clothing material due to its natural texture and unusual functions.
Cellulose fiber itself such as cellulose fiber and cotton fiber is most suitable for surgical operations and medical treatment in view of its excellent moisture absorbency, water absorbency, and flexibility. Recently, as a demand increases for prevention of bacterial infection in the affected body part and further prevention of internal infection such as MRSA in a hospital, characteristics of fiber material for surgical robes and bandages become more important. However, as described above, cotton fiber does not exhibit sufficient antibacterial effects since cotton is a natural material itself and its constituent components interfere with antibacterial effects. On the other hand, synthetic fiber possessing antibacterial effects does not have moisture and water absorbency, and thus are not suitable for medical use, and cannot satisfy the requirements for medical products. Accordingly, a demand for imparting antibacterial effects to cellulose fiber becomes intensifies.